This invention relates to dynamoelectric machines, and in particular, to a novel motor system which develops high torque, instantaneous rotation reversal and simple speed control.
For some time, motor manufacturers have attempted to develop new motor systems for use in high volume appliances. One such motor system is disclosed in a copending United States application of the present inventor, U.S. Ser. No. 395,187, filed Sept. 7, 1973, now U.S. Pat. No. 3,858,098. The system disclosed in Ser. No. 395,187, like the invention disclosed hereinafter, provides a motor system operable continuously in either of two directions of rotation and permits instantaneous reversal between those rotational directions. This type of operation is particularly suitable for certain high volume consumer appliances. Thus, the systems may find application in a conventional washing machine, where cyclic rotation reversal of the motor is equivalent to an agitation or washing mode, and the continuous unidirectional run condition of the motor corresponds to the spin dry cycle of the appliance. Because of the unique motor operating characteristics, the motor may be connected mechanically to drive the wash basket directly, eliminating the need for transmissions now commonly found in washing machine applications. The invention described hereinafter, while dealing broadly with the same subject matter as Ser. No. 395,187, exhibits a number of improvements over previously known electronically controlled motors, in both the motor and circuit design aspects of the system.
Other prior art dealing with electronically controlled motors include, for example, the SCR manual, Fourth Edition, 1967, published by the General Electric Company; Principles of Inverter Circuits, John Wiley and Sons, Inc., 1964, by B. D. Bedford and R. G. Hoft; Complimentary Impulse Commutator Inverter, by R. Young, Poughkeepskie Lab., Technical Report TROO, 1973, dated Jan. 30, 1973, I.B.M.; and the U.S. Patents to Greenwell, No. 3,780,324, issued Dec. 18, 1973, and Offutt, No. 3,802,091, issued Apr. 9, 1974.
While this body of prior art generally discloses the use of electronic circuit means for controlling the operation of a dynamoelectric machine, very little information presently is available relating a motor which is continuously reversing its direction of rotation as a normal mode of motor operation. Under general motor design principles, it is highly desirable that the per unit current torque, of both the unidirectional and the reverse braking varieties, be as high as possible. Besides the obvious desirable feature of high torque from the application standpoint, if high per unit current torque can be obtained, the SCR circuits utilized in conjunction with motor operation need not be designed for high current handling capabilities and the cost of the motor system can be reduced appreciably.
The invention dislosed hereinafter utilizes an SCR circuit for controlling the application of electrical energy to a motor. The motor itself has a unique winding designed to deliver high per unit current torque. A position sensor used in conjunction with the motor is provided which includes adjustable elements for adjusting the speed torque characteristic of the motor. In addition, the control circuitry disclosed incorporates a number of improvements including means for limiting the current rate of change seen by the individual SCR elements, and a novel circuit arrangement for providing dual outputs from a single electrical input which operate independently of one another.
One of the objects of this invention is to provide an improved motor control system.
Another object of this invention is to provide a circuit arrangement for providing signal source voltage and motor voltage independent from one another from a single electrical input.
Another object of this invention is to provide an improved SCR circuit for controlling application of electrical energy to a dynamoelectric machine.
Still another object of this invention is to provide a position sensing device and reversing mechanism which is adjustable to vary the speed torque characteristic of a motor.
Other objects of this invention will be apparent to those skilled in the art in light of the following description and accompanying drawings.